import React, { Component } from 'react';
import {
    Button,
    View,
    Text,
} from 'react-native'

class DetailsScreen extends React.Component {
  state={count:0};
  static navigationOptions = (props) => {
    const params = props.navigation.state.params;
    return {
      headerRight: (                        //通过params为按钮绑定increase方法
        <Button onPress={params.increase} title="+1" />
      ),
    };
  };

  componentWillMount() {                    //通过setParams将increase方法绑定到_increase
    this.props.navigation.setParams({ increase: this._increase });
  }
  _increase=()=>{                           //设置state.count+1
    this.setState(preState=>{return {count:preState.count+1}});
  };
  render() {
    return (
      <View >
        <Text>计数为：{this.state.count}</Text>
      </View>
    );
  }
}

export default DetailsScreen;
